Upright vacuum cleaners are generally provided with a height adjustment mechanism for varying the height of a chassis of a head assembly relative to a floor surface. The chassis carries a motor and fan and an agitator brush for brushing a floor surface to be cleaned. The distance the chassis and agitator brush are raised above a floor surface is dependent upon the type of floor surface to be cleaned. For example, if a linoleum or vinyl floor is being vacuumed, the agitator brush is spaced closely to the floor. In contrast, if a very deep pile carpet is being cleaned, the agitator brush is raised away from the floor surface to keep the agitator brush from binding with the individual strands of the carpet.
One popular technique of adjusting the relative height a chassis and agitator brush of a vacuum cleaner relative to a floor surface is to provide a movable variable height cam member intermediate the chassis and an axle or wheel retainer supporting front wheels. An example of a vacuum cleaner employing such a height adjustment mechanism is described U.S. Pat. No. 5,222,276, which has been incorporated herein by reference.
In that patent, a cam member has a pair of transversely spaced cam surfaces each having a series of varying height arcuate stepped cam surfaces. The stepped cam surfaces cooperate with a respective pair of cam followers formed on an axle retainer member supporting an axle and front wheels. The axle retainer member is pivotally attached to a chassis to rotate relative thereto about a transversely extending pivot axis. The pivoting of the axle retainer member and axle about the pivot axis will raise and lower the wheels relative to the chassis with the chassis, in turn, pivoting about a pair of back wheels. A knob is used to manually move the cam member from side to side. This causes different stepped cam surfaces to selectively engage the cam followers. Consequently, the axle retainer member pivots raising and lower the front wheels to one of a plurality of selected heights which is dependent upon the height of the individual stepped cam surfaces cooperating with the cam followers.
Inexpensive models of vacuum cleaners often provide only two or three different height adjustment settings of the chassis and agitator brush relative to a floor surface. More expensive or deluxe models, partially due to the need for product differentiation, generally provide for a greater number of height adjustment selections. Accordingly, different tooling and molds are required for the different height adjusting mechanisms of the different vacuum cleaners. This can result in significant tooling costs for creating a line of vacuum cleaners which have different numbers of height selection positions, particularly, if a series of complex molds need to be made for each model in the line of vacuum cleaners.
The present invention is intended to meet the need for providing height adjustment mechanisms for vacuum cleaners which provide for a wide selection of the number of possible height adjustment settings for different models at a low cost.